CN112099318B

CN112099318B - Exposure apparatus and article manufacturing method

Info

Publication number: CN112099318B
Application number: CN202010556563.4A
Authority: CN
Inventors: 漆原宏亮
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2019-06-18
Filing date: 2020-06-17
Publication date: 2024-01-02
Anticipated expiration: 2040-06-17
Also published as: CN112099318A; TW202101132A; TWI803747B; KR20200144483A; JP2020204739A; JP7213761B2

Abstract

The invention provides an exposure apparatus and an article manufacturing method. The correction performance and the productivity of the optical performance of the projection optical system are facilitated to be simultaneously achieved. The exposure device comprises: a projection optical system that projects a pattern of the mask onto the substrate; a supply unit configured to supply a mixed gas, in which a plurality of gases having different refractive indices are mixed at a preset mixing ratio, that is, a preset mixing ratio, to a space between optical elements in the projection optical system; and a control unit for correcting imaging characteristics of the projection optical system by controlling the set mixing ratio and exposing the substrate. The control section acquires response characteristics indicating the evolution of imaging characteristics when the supply section supplies the mixed gas at a fixed mixing ratio, and sets the set mixing ratio to a value obtained by correcting the target mixing ratio based on the response characteristics and exposes the substrate in a transition period before the imaging characteristics are changed to a steady state when the set mixing ratio is set to the target mixing ratio and exposes the substrate.

Description

Exposure apparatus and article manufacturing method

Technical Field

The present invention relates to an exposure apparatus and a method for manufacturing an article.

Background

With the recent development of high integration of semiconductor devices, the requirements for optical performance of exposure apparatuses are also increasing. As a factor that hinders improvement of the optical performance of the exposure apparatus, there is an example that the optical performance is affected by environmental changes such as air pressure changes and temperature changes inside and outside the projection optical system.

For such environmental changes, there is a method of supplying two or more gases having different refractive indices to a space in a projection optical system, and correcting magnification aberrations by changing the refractive index of the space by changing the mixing ratio of the gases (for example, patent documents 1 and 2).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 5-210049

Patent document 2: japanese patent laid-open No. 5-144700.

Disclosure of Invention

Problems to be solved by the invention

When the optical performance of the projection optical system is corrected by changing the mixing ratio of the gas, it takes a long time to displace the gas in the space of the projection optical system until the optical performance stabilizes. Conventionally, an exposure apparatus stops exposure and stands by until optical performance stabilizes. Therefore, the downtime of the exposure apparatus is long, and productivity is lowered.

The present invention aims to provide an exposure apparatus which is advantageous in, for example, both of correction performance and productivity of optical performance of a projection optical system.

Solution for solving the problem

According to a first aspect of the present invention, there is provided an exposure apparatus for exposing a substrate, the exposure apparatus comprising: a projection optical system that projects a pattern of a mask onto the substrate; a supply unit that supplies a mixed gas, which is obtained by mixing a plurality of gases having different refractive indices at a preset mixing ratio, that is, a preset mixing ratio, to a space between optical elements in the projection optical system; and a control section that corrects an imaging characteristic of the projection optical system and exposes the substrate by controlling the set mixing ratio, the control section acquiring a response characteristic indicating an evolution (change) of the imaging characteristic when the supply section supplies a mixed gas at a fixed mixing ratio, the control section setting the set mixing ratio to a value obtained by correcting the target mixing ratio based on the response characteristic and exposing the substrate in a transition period before the imaging characteristic is shifted to a steady state when the set mixing ratio is set to the target mixing ratio and exposes the substrate.

According to a second aspect of the present invention, there is provided a method of manufacturing an article, comprising: a step of exposing a substrate using the exposure apparatus according to the first aspect; and developing the exposed substrate, wherein an article is manufactured from the developed substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, for example, an exposure apparatus that is advantageous in terms of both correction performance and productivity of optical performance of a projection optical system can be provided.

Drawings

Fig. 1 is a diagram showing a configuration of an exposure apparatus in the embodiment.

Fig. 2 is a flowchart showing exposure processing accompanied by correction of optical performance of the projection optical system in the embodiment.

Fig. 3 is a graph showing an example of response characteristics of aberrations in the mixed gas substitution.

Fig. 4 is a diagram showing a proportional relationship that exists between the amount of change in spherical aberration and the change in the mixing ratio of the mixed gas.

Description of the reference numerals

1: an exposure device; 2: a lighting system; 3: a mask; 5: a projection optical system; 9: a substrate table; 10: a substrate; 25: a control unit; 30: and a supply unit.

Detailed Description

Hereinafter, embodiments will be described in detail with reference to the drawings. The present embodiment described below is not intended to limit the invention according to the claims. In the present embodiment, a plurality of features are described, but not all of these features are essential to the invention, and a plurality of features may be arbitrarily combined. In the drawings, the same or similar structures are denoted by the same reference numerals, and repetitive description thereof will be omitted.

Fig. 1 is a diagram showing a configuration of an exposure apparatus 1 in the present embodiment. In one example, the exposure apparatus 1 is an exposure apparatus that exposes a pattern of the mask 3 to the substrate 10 in a step and repeat (step and repeat) manner. However, the present invention can also be applied to a step and scan (step and scan) system and other exposure apparatuses.

The illumination system 2 adjusts light from a light source, not shown, such as a mercury lamp having a wavelength of about 365nm, a KrF excimer laser having a wavelength of about 248nm, or an ArF excimer laser having a wavelength of about 193nm, and illuminates the mask 3. The mask 3 is made of, for example, quartz glass, and has a pattern (for example, a circuit pattern) to be transferred onto the substrate 10. The mask stage 4 can hold the mask 3, and adjust at least one of the position and the posture of the mask 3 by, for example, a linear motor. The driving of the mask stage 4 is controlled by the control unit 25.

The projection optical system 5 projects the pattern of the mask 3 onto the substrate 10 at a predetermined magnification (for example, 1/4). The substrate 10 is a substrate formed of, for example, a glass plate (glass plate), a Silicon wafer (Silicon wafer), or the like. The surface of the substrate 10 is coated with a photosensitive agent 11. The projection optical system 5 includes a plurality of optical elements 6 (e.g., optical elements such as lenses (lenses), mirrors (mirrors), aperture stops, and the like). At least one of the position, posture, shape, and temperature of a part of the plurality of optical elements 6 can be adjusted by the adjusting section 7.

The substrate stage 9 can hold the substrate 10, and adjust at least one of the position and the posture of the substrate 10 by, for example, a linear motor. The driving of the substrate table 9 is controlled by the control unit 25. The laser interferometer 14 is disposed near the substrate stage 9, and measures the position of the substrate stage 9 by directing laser light to a bar mirror (bar mirror) 12 disposed on the substrate stage 9.

The exposure apparatus 1 includes a supply unit 30, and the supply unit 30 supplies a mixed gas obtained by mixing a plurality of gases having different refractive indices to a space between optical elements in the projection optical system 5. In the supply unit 30, the gas supply units 15 and 16 supply a plurality of gases having different refractive indices to the mixer 19. The plurality of gases may be, for example, a plurality of gases selected from helium, nitrogen, oxygen, carbon dioxide, dry air, and the like. The gas supply amount adjusters 17 and 18 adjust the supply amounts of the gases from the gas supply portions 15 and 16, respectively. The mixer 19 mixes at least two different gases supplied from the gas supply units 15 and 16, and supplies the mixed gas to the projection optical system 5 via the gas supply pipe 21. The concentration measuring device 20 measures the concentration of each gas in the mixed gas. Such a supply unit 30 can supply a mixed gas mixed at a preset mixing ratio, that is, a preset mixing ratio.

The mixed gas supplied to the projection optical system 5 is diffused into the space between the optical elements via the vent hole 8 provided in the adjustment portion 7 supporting the optical element 6. The vent hole 8 may be a member not shown in the drawings that fixedly supports the optical element 6, instead of the adjustment portion 7. The exhaust unit 22 discharges the gas from the projection optical system 5 through an exhaust pipe 24. The exhaust pipe 24 is provided with an exhaust gas amount adjusting portion 23 for adjusting the amount of exhaust gas to be discharged from the exhaust portion 22. The control unit 25 controls the exhaust gas amount adjustment unit 23 based on the air pressure value measured by the air pressure gauge 26 to adjust the exhaust gas amount so as to eliminate the air pressure difference between the inside and outside of the projection optical system 5.

The detector 13 detects the light transmitted from the projection optical system 5. The detector 13 can include, for example, at least any one of an interferometer and a light intensity sensor. The control section 25 can measure wavefront aberration at each point in the exposure area of the projection optical system 5 based on the detection result of the detector 13. The control unit 25 can also measure the distortion aberration of the projection optical system 5 based on the detection result of the detector 13. Here, the distortion aberration is, for example, an amount indicating how much the actual image height on the image plane deviates from the ideal image height, and can be measured at each point on the image plane (in the exposure region). The detector 13 may have any known structure, and thus a detailed description of the structure and operation is omitted here.

The adjustment unit 7 adjusts the imaging characteristics, and here, for example, adjusts at least one of the position, posture, shape, and temperature of a part of the plurality of optical elements 6 of the projection optical system 5. The adjustment unit 7 includes, for example, a mechanism that drives in the optical axis direction (Z direction shown in fig. 1) and a direction perpendicular to the optical axis direction, a mechanism that drives a support portion that supports the optical element, a mechanism that applies stress to the optical element (force that presses or pulls the optical element), a mechanism that heats or cools the optical element, and the like. These drives in the adjustment section 7 are controlled by the control section 25. However, the adjustment unit may adjust the imaging characteristics by performing at least one of driving the optical element 6 of the projection optical system 5, driving the mask stage 4, and driving the substrate stage 9.

The control unit 25 comprehensively controls the operations of the respective parts of the exposure apparatus 1. The control section 25 may be constituted by a computer including a CPU and a memory. In the present embodiment, the control unit 25 functions as a control unit that corrects the imaging characteristics of the projection optical system 5 and exposes the substrate by controlling the mixing ratio set in the supply unit 30. The control unit 25 calculates the adjustment amount of the optical element 6 and the adjustment amount of the substrate stage 9 by the adjustment unit 7 based on the detection result of the detector 13, and controls the adjustment unit 7 and the substrate stage 9 based on the calculated adjustment amount of the optical element 6 and the calculated adjustment amount of the substrate stage 9.

The exposure process of the optical performance (imaging characteristics) of the projection optical system 5 in the present embodiment will be described below. The index representing the imaging characteristics includes a plurality of aberration components. For example, the imaging characteristics may include at least one of spherical aberration, magnification aberration, distortion aberration, curvature of field, astigmatism, coma. In order to illustrate a specific example, spherical aberration, which is a first aberration component among a plurality of aberration components, is set as a correction target. Further, as other aberration components than the first aberration component, it is conceivable that magnification aberration and distortion aberration are generated.

In the correction processing in the present embodiment, the control section 25 acquires in advance a response characteristic indicating the evolution of the imaging characteristic when the mixed gas is supplied by the supply section 30 at a fixed mixing ratio. When the control section 25 sets the set mixture ratio to the target mixture ratio to expose the substrate, the control section 25 sets the set mixture ratio to a value in which the target mixture ratio is corrected based on the response characteristic and exposes the substrate in a transition period before the imaging characteristic is shifted to the steady state. Fig. 2 is a flowchart showing a specific example of such exposure processing. In S101, the control section 25 acquires a response characteristic indicating the evolution of the imaging characteristic when the mixed gas is supplied by the supply section 30 at a fixed mixing ratio. Here, the data of such response characteristics are obtained by measurement or simulation in advance, and are stored in the memory of the control unit 25.

In the present embodiment, the response characteristics can include response characteristics related to spherical aberration, magnification aberration, and distortion aberration, respectively. Fig. 3 shows examples of these response characteristics. The response characteristic referred to herein indicates the evolution of the aberration (change in aberration with respect to displacement time) when the mixed gas is supplied by the supply unit 30 at a fixed mixing ratio. (a) is an example of response characteristics of spherical aberration, (b) is an example of response characteristics of magnification aberration, and (c) is an example of response characteristics of distortion aberration. Even if the purge gas is supplied into the projection optical system, the entire space cannot be replaced immediately, and such response characteristics are exhibited. For example, as shown in (a), spherical aberration may have an unstable period (transition period) before becoming stable. The data of the acquired response characteristics are stored in a memory, not shown, of the control unit 25.

In S102, the control unit 25 measures a change in the amount of aberration caused by exposure. For example, the projection optical system 5 absorbs exposure energy in association with exposure, and thus imaging characteristics change (exposure aberration). Then, the control unit 25 can determine the correction amount by applying the detection result of the detector 13 to a predetermined predictive expression to predict the fluctuation of the imaging characteristic (spherical aberration in this case). Alternatively, the control unit 25 may measure a change in aberration with respect to the exposure heat generated under each illumination condition based on the detection result of the detector 13. The control unit 25 measures the atmospheric pressure of the space in which the projection optical system 5 is provided, using the barometer 26.

In S103, the control unit 25 obtains a refractive index for compensating the aberration variation obtained in S102, and determines a target mixing ratio corresponding to the refractive index. The correspondence between the refractive index and the target mixing ratio is previously defined by a mathematical formula or a table. The control unit 25 may calculate the amount of spherical aberration generated due to the influence of the change in the atmospheric pressure based on the value of the atmospheric pressure measured in S102, and add the calculated amount to the correction amount. As a method for determining the amount of spherical aberration generated by the change in the atmospheric pressure, there is a method of obtaining the amount of spherical aberration by, for example, the product of the atmospheric pressure sensitivity coefficient and the amount of change in the atmospheric pressure, which is calculated by measuring the amount of change in the spherical aberration with respect to the change in the atmospheric pressure.

The mixing ratio is determined, for example, as follows. The amount of change in the spherical aberration with respect to the change in the mixing ratio of the mixed gas (i.e., the change in refractive index) is a proportional relationship shown in fig. 4. Based on this relationship, the proportionality constant of the spherical aberration amount with respect to the refractive index of the lens space of the projection optical system can be calculated by optical simulation. The control unit 25 may predict the amount of spherical aberration of the projection optical system 5 generated by exposure heat under the illumination condition used for exposure based on the change in the aberration measured in S102, and add the amount to the correction amount.

The following processing is processing when the substrate is exposed by setting the set mixture ratio to the target mixture ratio determined here.

In S104, the control unit 25 determines the allowable range (correctable range) of each of the magnification aberration and the distortion aberration, which are other aberration components, in the mixed gas substitution. Such a correctable range may be defined in advance in the exposure process.

In S105, the control unit 25 starts gas supply and exhaust control of the projection optical system 5. Specifically, the control unit 25 adjusts the gas supply amount adjusters 17 and 18 in accordance with the target mixing ratio determined in S103, and adjusts the flow rate of the gas flowing into the mixer 19. The gas mixed by the mixer 19 is supplied to the projection optical system 5 while the amount of the gas is adjusted by the amount adjustment unit 23 so that the pressure difference between the inside and outside of the projection optical system 5 does not occur. Thereby, spherical aberration is corrected.

In S106, the control unit 25 carries in (loads) the substrate to be exposed by a conveying mechanism not shown. The loaded substrate is held by the substrate stage 9.

In S107, the control section 25 determines whether or not the current point in time is in the transition period before the imaging characteristic (here, spherical aberration) is shifted to the steady state. In the case where the transient period is in progress, in S108, the control section 25 sets the set mixing ratio to a value obtained by correcting the target mixing ratio based on the response characteristic. Specifically, the amount of aberration corresponding to the current time is found from the response characteristic of the spherical aberration obtained in S101 ((a) of fig. 3), and the target mixing ratio is corrected by the correction amount corresponding to the amount of aberration. As described above, in the present embodiment, the target mixing ratio of the mixed gas is actively corrected.

However, in the case where such an active correction is performed on the mixing ratio, other aberration components may be newly generated, and thus correction thereof may be also required. The other aberration components are corrected by the adjusting section 7 within a range not exceeding the correctable range thereof. Then, in S109, the control section 25 determines whether or not the other aberration component is within the allowable range (correctable range) determined in S104. When the other aberration component is within the allowable range, the control unit 25 controls the adjustment unit 7 to correct the other aberration component in S110. When the other aberration component changes beyond the correctable range of the adjusting section 7, the exposure is stopped (S111) until the adjusting section 7 can perform correction. At this time, the supply of the mixed gas may be continued until the correctable range is reached, and the exposure of the exposure apparatus 1 may be stopped during this period. When the current time point is the steady state period after the transition period has elapsed (no in S107), the control unit 25 sets the set mixing ratio to the target mixing ratio determined in S103 in S112.

Thereafter, in S113, the control unit 25 performs exposure to the substrate. After the exposure is completed, in S114, the control unit 25 controls the conveyance mechanism to carry out the substrate (unload). In S115, the control unit 25 determines whether or not there is a substrate to be processed. If there is a substrate, the process returns to S102 and the process is repeated. When the predetermined processing of all the substrates is completed, the present processing is ended.

In the above example, the mixed gas was supplied for correcting spherical aberration, but the object of correction may be magnification aberration, distortion aberration, curvature of field, astigmatism, coma, or the like. In the above example, the other aberration components corrected by the adjustment unit 7 are magnification aberration and distortion aberration, but spherical aberration, curvature of field, coma aberration, and the like may be used.

According to the above processing, as long as the other aberration components (magnification aberration and distortion aberration) do not exceed the correctable range of the adjusting section 7, a desired spherical aberration can be obtained without stopping the exposure processing. Thus, the correction performance of the optical performance of the projection optical system and the productivity can be simultaneously achieved.

Embodiment of article manufacturing method

The method for manufacturing an article according to the embodiment of the present invention is suitable for manufacturing an article such as a microdevice such as a semiconductor device or an element having a precise structure. The method for producing an article according to the present embodiment includes a step of forming a latent image pattern on a photosensitive agent coated on a substrate using the exposure device (step of exposing the substrate); and developing the substrate on which the latent image pattern is formed in the above step. The production method includes other known steps (oxidation, film formation, vapor deposition (japanese: vapor deposition), doping, planarization, etching, resist stripping, dicing, bonding, packaging, and the like). The method for manufacturing an article according to the present embodiment is advantageous in at least one of performance, quality, productivity, and production cost of the article, as compared with the conventional method.

The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the claims are appended to disclose the scope of the invention.

Claims

1. An exposure apparatus for exposing a substrate, the exposure apparatus comprising:

a projection optical system that projects a pattern of a mask onto the substrate;

a supply unit that supplies a mixed gas, which is obtained by mixing a plurality of gases having different refractive indices at a preset mixing ratio as a preset mixing ratio, to a space between optical elements inside the projection optical system; and

a control section that corrects imaging characteristics of the projection optical system and exposes the substrate by controlling the set mixing ratio,

the control section acquires a response characteristic indicating an evolution of the imaging characteristic when the mixed gas is supplied by the supply section at a fixed mixing ratio,

the control section sets the set mixture ratio to a value obtained by correcting the target mixture ratio based on the response characteristic and exposes the substrate in a transition period before the imaging characteristic is shifted to a steady state when the set mixture ratio is set to the target mixture ratio and exposes the substrate.

2. The exposure apparatus according to claim 1, wherein,

after the transition period has elapsed, the control section sets the set mixture ratio to the target mixture ratio and exposes the substrate.

3. The exposure apparatus according to claim 1, wherein,

and an adjusting section that adjusts the imaging characteristic,

the control section corrects a first aberration component, which is the imaging characteristic, among a plurality of aberration components by controlling the set mixing ratio,

the adjustment unit corrects other aberration components than the first aberration component, which are the imaging characteristics, in response to the setting mixing ratio being changed by the control unit during the transition period.

4. The exposure apparatus according to claim 3, further comprising:

a mask stage that holds the mask; and

a substrate stage holding the substrate,

the adjustment unit adjusts the imaging characteristic by performing at least one of driving an optical element of the projection optical system, driving the mask stage, and driving the substrate stage.

5. The exposure apparatus according to claim 3, wherein,

when the correction amount for the other aberration component exceeds the correctable range of the adjustment portion, the control portion stops the exposure of the substrate until the adjustment portion can perform correction.

6. The exposure apparatus according to claim 3, wherein,

the imaging characteristics include at least one of spherical aberration, magnification aberration, distortion aberration, curvature of field, astigmatism, and coma.

7. The exposure apparatus according to claim 3, wherein,

the first aberration component is spherical aberration, and the other aberration components are magnification aberration and distortion aberration.

8. The exposure apparatus according to claim 7, wherein,

the response characteristics include response characteristics related to spherical aberration, magnification aberration, and distortion aberration, respectively.

9. The exposure apparatus according to claim 1, wherein,

the plurality of gases are a plurality of gases selected from helium, nitrogen, oxygen, carbon dioxide, dry air.

10. The exposure apparatus according to claim 1, wherein,

and a barometer that measures an atmospheric pressure of a space in which the projection optical system is provided,

the control unit obtains a change amount of the imaging characteristic due to an influence of a change in the atmospheric pressure based on the value of the atmospheric pressure measured by the barometer, and obtains a correction amount for the imaging characteristic based on the change amount.

11. The exposure apparatus according to claim 1, wherein,

and a detector for detecting light transmitted through the projection optical system,

the control unit obtains a change amount of the imaging characteristic due to absorption of the exposure energy by the projection optical system by the detector, and obtains a correction amount for the imaging characteristic based on the change amount.

12. A method of manufacturing an article, comprising:

a process of exposing a substrate using the exposure apparatus according to any one of claims 1 to 11; and

a step of developing the exposed substrate,

wherein an article is manufactured from the developed substrate.